With advancement of densification of hard disks, the floating amount of the magnetic head has become increasingly smaller. As a result, in the polishing step in hard disk substrates, there have been desired increase in the polishing rate and reduction in the surface roughness. Therefore, a polishing composition using water, alumina, boehmite, and a chelating compound, and a polishing process have been studied (Japanese Patent Laid-Open No. Hei 11-92749). However, this polishing composition has some but insufficient effects for increasing the polishing rate and for reducing surface defects such as scratches and pits. Also, its effects cannot also be said to be satisfactory for reduction in the surface roughness and for the planarization.
Also, even in the field of semiconductors, the finely sizing of a design room for a semiconductor device has been progressed with the advancements in high integration and high speeds, so that a focal depth becomes shallow during the process for manufacturing the device, whereby further demanding planarization of the pattern-forming surface.